(a) Technical Field of the Invention
The present invention relates to a dual-contact tool holder for a lathe/miller, and in particular to a tool holder that provides dual side constraint forces in fixing a tool rest so as to enhance the fixing of the tool rest.
(b) Description of the Prior Art
Prosperity of economy brings the progress of industrial technology. To improve market competitiveness, every manufacturer in every industry spends a lot of effort and cost in development and research. For machining operation, lathes and milling machines are almost a must and are often employed to perform various turning and milling based machining operations. These machine tools are operated by fixing, in a position adjustable manner, a tool or cutter with respect to a work piece by a tool holder device, an example of which is illustrated in FIG. 1 of the attached drawings, wherein a draw bar 12 is provided at an end of a ram 11 to couple a tool seat 13 and a tool rest 14 is fixed to the underside of the tool seat by bolts. Hydraulic force is employed to drive the ram 11, which in turn causes the draw bar 12 to move the tool seat 13 up and down. Such a device is effective in fixing or holding the tool rest 14, but since the draw bar 12 of the ram 11 is operated by hydraulic power, which although providing a substantially constant force in carrying out the operation, is subjected to certain compressibility, which leads to minor discrepancy. Consequently, minor difference of force may occur on the tool rest during a turning or milling operation, affecting the precision of the machining operation. FIG. 2 of the attached drawings illustrates another known tool holder, wherein a tool seat 22 has an extension that forms a reduced coupling section 23 by which the tool seat 22 is coupled to a ram 21 located above, and a tool rest 24 is coupled to the underside of the tool seat 22 by bolts. By being driven by the ram 21, the tool seat 22 is caused to displace, which in turn leads to displacement of the tool rest 24 for carrying out turning or milling operation. Such a known tool holder provides only a reduced drawing force due to the reduced dimension of the coupling section 23, and as a consequence, the operation of turning or milling is affected. Apparently, this is a device that can be further improved. To conclude, both known tool holders discussed above are desired to be further improved.